Trabalhar com o IIS 7.5 é um pouco assustador quando se trata dos novos nomes de host virtuais para servidores FTP. No entanto, mesmo que pareça que você configurou o servidor do yoru IIS 7.5 corretamente, IE, Chrome e outros navegadores para não saber como lidar com esse tipo de solicitações de host virtual da mesma maneira que o seu IIS 7.5 pode lidar com isso.
O único trabalho atualmente disponível é fazer o seguinte, citado:
Internet Explorer, Windows Explorer and Virtual FTP Sites issue
Both the Internet Explorer and Windows Explorer first try to connect to FTP server anonymously. If they fail, then they prompt for credentials.When FTP 7 is only configured with virtual host name based sites, these clients fail. Anonymous logon will be be rejected by server the way, that is valid as far as FTP specification (RFC 959) goes, nonetheless, it confuses the authentication sequence of those clients. Robert McMurray, noticed the problem long time ago and proposed a simple workaround in the following blog http://blogs.msdn.com/robert_mcmurray/archive/2008/12/17/ftp-clients-part-3-creating-a-global-listener-ftp-site.aspx.
To address the problem, you would need to create a GlobalListenerFtpSite, that is not configured with a host name. It has to deny anonymous access. As a matter of fact you should not allow any access to the site (leave the authorization section empty). This site will reject the anonymous logon the way that is friendly to IE and Windows Explore. Everything will then work as expected. Robert's blog entry will provide more information on the topic.
Você pode encontrar mais informações detalhadas a partir do artigo a seguir e escrever: Solucionando o problema do separador" | "para sites FTP virtuais (FTP 7.5).